From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 12 Sep 2007 16:51:38 +0900 From: KAMEZAWA Hiroyuki Subject: Re: [PATCH 4/6] Embed zone_id information within the zonelist->zones pointer Message-Id: <20070912165138.5deb4db4.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20070911213127.23507.34058.sendpatchset@skynet.skynet.ie> References: <20070911213006.23507.19569.sendpatchset@skynet.skynet.ie> <20070911213127.23507.34058.sendpatchset@skynet.skynet.ie> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Mel Gorman Cc: Lee.Schermerhorn@hp.com, akpm@linux-foundation.org, ak@suse.de, clameter@sgi.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: On Tue, 11 Sep 2007 22:31:27 +0100 (IST) Mel Gorman wrote: > Using two zonelists per node requires very frequent use of zone_idx(). This > is costly as it involves a lookup of another structure and a substraction > operation. As struct zone is always word aligned and normally cache-line > aligned, the pointer values have a number of 0's at the least significant > bits of the address. > > This patch embeds the zone_id of a zone in the zonelist->zones pointers. > The real zone pointer is retrieved using the zonelist_zone() helper function. > The ID of the zone is found using zonelist_zone_idx(). To avoid accidental > references, the zones field is renamed to _zones and the type changed to > unsigned long. > At first, I welcome this patch. thanks!. A comment after reading all is, how about defining zonelist as following instead of encoding in pointer ? == struct zone_pointer { struct zone *zone; int node_id; int zone_idx; }; struct zonelist { struct zone_pointer _zones[MAX_ZONES_PER_ZONELIST + 1]; }; #define zonelist_zone(zl) (zl)->zone #define zonelist_zone_idx(zl) (zl)->zone_idx #ifdef CONFIG_NUMA #define zonelist_zone_nid(zl) (zl)->node_id #else #define zonelist_zone_nid(zl, i) (0) == If we really want to avoid unnecessary access to "zone" while walking zonelist, above may do something good. Cons is this makes sizeof zonlist bigger. Thanks, -Kame -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org